It has been suggested on other sites that if a 40 odd foot boat is pitching in an anchorage, this might be reduced by hanging a bag of rocks off the stern and possibly the bow also.
Just off the top of my head, I would guess that this bag would need to weigh a thousand pounds or more to have much effect, if any.
Can one of you really, really smart engineering types on here chime in with a bit of fact based information on this, please. Thank you.

It has been suggested on other sites that if a 40 odd foot boat is pitching in an anchorage, this might be reduced by hanging a bag of rocks off the stern and possibly the bow also.

Oh my.

I don't think weight would help. After all, we try to reduce weight in the ends to reduce pitching moment. You could talk me into a bucket that provides resistance to motion without significant weight.

Please do not try to discredit this hypothesis. I would very much enjoy being at anchor watching people tote a thousand pounds of rocks in their dinghies in the sort of conditions likely to create unpleasant pitching.

In order to reduce the pitching movement of the boat you need to re-arrange your load distribution, placing proportionately more weight aft. Think of it as a hobbyhorse, where a fat guy sits in the back.

The idea is not as bad as some of you want it to be. Those active in sailing some 3-4 decades ago may remember that about the same theory was quoted when pitching was to heavy during sailing - the cure was said to put something heavy (as a crew member) at the crosstrees in the mast.
And it worked - sometimes.

When pitching heavily there is a resonance, caused by wind, waves and the boat, mainly its moment of inertia. The moment of inertia can be changed be re-distribute weights on the boat, which might move the boat out of resonance with the waves & wind.
To this one should also note that the moment of inertia is proportional to the mass (weight) * r*r where r is the distance between the centre and the centre of the weight (google Steiners theorem if you want to know more). Thus ... distance is more important than weight, the further out the more moment of inertia is changed.

No 1000 pound is needed to make this change on a 40 ft boat. It is often perfectly enough with some few 100 pounds ... conclusion is given, eeh?

Now, all this is nice. In reality sea waves are not of one frequency, but have a wide distribution (a wide normal distribution if anything). In order to really avoid resonance effects, moment of inertia should be changed rather dramatically. So, these few 100 pounds, could they be kind enough to move up to the top of the mast?

OK, if all this works out well, what happens then when wind changes? Oh, new possibilities for resonances!

There are other methods, actually. But weights work, in theory and practice.

Reducing the distance the bow rises up, will lessen its fall.
So in cabin weight should go forward even if it lightens the stern. The stern never has a pitching problem.
You may want to try hanging an empty, wide lipped bucket ,from the bow chain. Place it up to 3' from the bow to avoid contact, and low enough that the bucket never rises above the sea during the pitch up. It should dampen the initial pitch.

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register. Please enter your desired user name, your email address and other required details in the form below.Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.

User Name:

Password

Please enter a password for your user account. Note that passwords are case-sensitive.

Password:

Confirm Password:

Email Address

Please enter a valid email address for yourself.

Email Address:

OR

Log-in

User Name

Password

Remember Me?

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.